In casting gas turbine engine blades and vanes using conventional equiaxed and directional solidification techniques, ceramic cores are positioned in an investment shell mold to form internal cooling passageways. During service in the gas turbine engine, cooling air is directed through the passageways to maintain blade temperature within an acceptable range. In manufacture of large gas turbine engine blades and vanes for industrial gas turbine engines, correspondingly larger ceramic cores are used to form the internal passages. The ceramic cores used in investment casting can be prone to distortion and loss of the required dimensional tolerance during core manufacture, especially of the airfoil core pitch. The problem of airfoil pitch distortion is greater for larger ceramic cores used in the manufacture of industrial gas turbine engines.
An object of the present invention is to provide a method of making a ceramic core and the core so made in a manner that reduces airfoil pitch shrinkage and loss of dimensional tolerance.